преобразование кода в читабельный вид

function SymbolReplace ($msg) {
$msg = strtoupper ($msg);
return strtr($msg, array("\U0430"=>"а", "\U0431"=>"б", "\U0432"=>"в",
"\U0433"=>"г", "\U0434"=>"д", "\U0435"=>"е", "\U0451"=>"ё", "\U0436"=>"ж", "\U0437"=>"з", "\U0438"=>"и",
"\U0439"=>"й", "\U043A"=>"к", "\U043B"=>"л", "\U043C"=>"м", "\U043D"=>"н", "\U043E"=>"о", "\U043F"=>"п",
"\U0440"=>"р", "\U0441"=>"с", "\U0442"=>"т", "\U0443"=>"у", "\U0444"=>"ф", "\U0445"=>"х", "\U0446"=>"ц",
"\U0447"=>"ч", "\U0448"=>"ш", "\U0449"=>"щ", "\U044A"=>"ъ", "\U044B"=>"ы", "\U044C"=>"ь", "\U044D"=>"э",
"\U044E"=>"ю", "\U044F"=>"я", "\U0410"=>"А", "\U0411"=>"Б", "\U0412"=>"В", "\U0413"=>"Г", "\U0414"=>"Д",
"\U0415"=>"Е", "\U0401"=>"Ё", "\U0416"=>"Ж", "\U0417"=>"З", "\U0418"=>"И", "\U0419"=>"Й", "\U041A"=>"К",
"\U041B"=>"Л", "\U041C"=>"М", "\U041D"=>"Н", "\U041E"=>"О", "\U041F"=>"П", "\U0420"=>"Р", "\U0421"=>"С",
"\U0422"=>"Т", "\U0423"=>"У", "\U0424"=>"Ф", "\U0425"=>"Х", "\U0426"=>"Ц", "\U0427"=>"Ч", "\U0428"=>"Ш",
"\U0429"=>"Щ", "\U042A"=>"Ъ", "\U042B"=>"Ы", "\U042C"=>"Ь", "\U042D"=>"Э", "\U042E"=>"Ю", "\U042F"=>"Я")
);
}

$str='\U0430\U0431\U0432\U0433';
$ar=explode('\U',$str);
for($i=1;$i<count($ar);++$i){
$n.='&#'.base_convert($ar[$i],16,10);
}
echo html_entity_decode($n, ENT_NOQUOTES,'UTF-8');

print_r(json_decode('{"t":"\u043C\u0430\u0442\u044C"}'));

$str='\u043C\u0430\u0442\u044C';
echo html_entity_decode(str_replace('\u','&#x',$str), ENT_NOQUOTES,'UTF-8');